The present invention relates to a miter saw, and more particularly, to such a miter saw having an angularly rotatable turntable, and a circular saw unit laterally tiltable relative to the turntable.
Japanese Patent Application Publication No. 2000-254817 discloses a miter saw including a base section, a support section, and a circular saw unit. The base section includes a base and a turntable mounted on the base and rotatable about its axis. A workpiece is mounted on the turntable. The support section upwardly extends from the turntable and laterally tiltable. The circular saw unit is positioned above the base section and is pivotally movably supported to the support section. The circular saw unit includes a circular saw blade and a motor for rotating the blade.
For angled cutting, the turntable is angularly rotated about its axis to change the angle of the side surface of the circular saw blade relative to a fence. For slant cutting, the support section is laterally tilted to change the angle of the side surface of the circular saw blade relative to the upper surface of the turntable.
According to up to date electronic technology, it may be conceivable that a digital display portion is provided in the miter saw so as to display an angular rotation angle of the turntable and a tilting angle of the circular saw blade. To this effect, the miter saw must include detection units for detecting a rotation angle of the turntable and a tilting angle of the support section.
As a rotation amount detection unit, an optical sensor unit is conceivable. For example, the optical sensor unit includes a light emitting element, a disc like element, and an optical sensor. The disc like detected element is rotatable in synchronism with the rotation of the turntable and is formed with a plurality of slits arrayed in a circumferential direction of the disc and spaced away from each other by a constant distance in the circumferential direction. The disc like element generates optical pulse each time the light passes through each slit and non slit region shuts off the light. The optical pulse is detected by the optical sensor. If slit distance is configured to generate a single pulse as a result of rotation of the turntable by 0.05 degrees, 900 pulses are theoretically generated if the turntable is angularly rotated from 0 degree to 45 degrees. Such arrangement would be also available for a tilting amount detection unit.
Renewal of the display of the rotation angle of the turntable at the rate of 0.05 degrees in the digital display appears to be too minute. Therefore, renewal of the display at a unit rate of 0.2 degrees appears to be comprehensive or intuitive for the user. For example successive angle display in the order of 34.8, 35.0, 35.2 . . . are conceivable.
Similarly, renewal of the display of the tilting angle of the circular saw blade at the rate of 0.05 degrees in the digital display appears to be too minute. Therefore, renewal of the display at a unit rate of 0.5 degrees appears to be comprehensive or intuitive for the user. For example successive angle display in the order of 34.0, 34.5, 35.0 . . . are conceivable.
However, display of the angles at an integral multiple of the unit rate only may cause another disadvantage. For example, laid open Japanese Patent Application Publication No. H11-254401 discloses a miter saw for cutting a workpiece at a specific angular rotation angle of the turntable and at a specific tilting angle of the circular saw blade for providing an artificial building material such as a molding member which is a decorative member to be obliquely spanned at a corner region, for example between a ceiling and a vertical wall. To attain the cutting, typical specific angular rotation angles of the turntable such as 22.5 35.5 and typical specific tilting angles of the circular saw blade such as 33.9 must be displayed.